This invention is directed generally to the tinting or coloration of contact lenses for human eyes, and more particularly to a novel method for carrying out such tinting.
In recent years, the so-called "soft" contact lenses have met with widespread acceptance. Such soft contact lenses are manufactured from a hydrophilic plastic material; that is, they can absorb and retain water, and become soft and pliable upon absorption of water. They are therefore relatively comfortable for the user to wear and can be worn for relatively long periods of time.
Tinted or colored soft contact lenses have additional advantages or attractions to many contact lens wearers. For example, tinted lenses may be desired for cosmetic reasons by patients. Such cosmetic improvement may be particularly advantageous in the case where the patient's eyes have been discolored or disfigured by illness or accident. Such tinted lenses may also be advantageously used by patients with diplopia to make the eyes appear more normal. Similarly, such tinted lenses may provide albino and aniridic patients with improved general ocular and facial appearances. Tinted lenses may also be utilized to reduce light transmission and enhance visual comfort in the presence of high light levels.
A number of methods of coloring the central areas of contact lenses have been suggested, for example in U.S. Pat. No. 4,252,421 to Foley, Jr. However, the tinting or coloration of contact lenses is not a simple task. In this regard, it is important that the tinted or colored lens provide a natural appearance in the wearer's eye. Thus, the tinted lens should preferably have a clear central area, a colored intermediate area and a clear outer area so that the colored portion will not cover the sclera of the eye. However, in cases where it is desired to further reduce light transmission, the central portion may be colored or tinted as well. Generally then, it is desirable to be able to provide the lens with a circular and preferably annular tinted area surrounded by clear, untinted lens material, so as to generally correspond to the normal appearance of the eye.
In manufacturing such a tinted lens, several problems can arise with respect to mounting the lens on a tinting fixture. U.S. Pat. No. 4,518,390 to Richard Rabenau and Jeffery Allen Ryder discloses one particularly advantageous such tinting fixture. The tinting fixture disclosed in this patent advantageously alleviates problems associated with handling of the lens during tinting or coloration thereof. Advantageously, this fixture readily centers and mounts the lens thereupon automatically to obtain the desired ring-like or annular pattern of tinting, while maintaining relatively sharp borders or edges intermediate tinted and untinted portions of the lens. In this regard, it will be appreciated that maintaining a clearly defined area of coloration is important since even slight fuzziness or running of dye colors into uncolored areas of the lens will be immediately apparent. Such fuzziness or tint runs will necessitate the rejection of the finished lens product.
Heretofore the process of tinting lenses was carried out exclusively in lens manufacturing facilities utilizing relatively complex, expensive and sophisticated equipment. Moreover, operation of this equipment required relatively skilled, highly trained technicians or operators.
Such tinting of lenses generally involves placement of the lens on a fixture as discussed above, and thereafter applying a predetermined amount of heat energy to the lens to enhance the setting or fixing of the dye thereupon. Thereafter a number of operations must be carried out in sequence, including, after initially applying a suitable dye thereto, allowing a period of time to allow the dye to set. This dye is applied to the interior surface of the lens and allowed to permeate during the ensuing period into the pores of the material. Thereafter, several additional chemical agents must be utilized in sequence to complete the dyeing or tinting process.
Initially, following application of the dye and the setting or initial drying period, a sodium nitrite solution, preferably of 5% concentration, is applied to the lens. Immediately thereafter, a dilute sulfuric acid solution also of substantially 5% concentration is applied. In response to application of the sulfuric acid, which acts as an oxydizing agent, the water soluble dye precipitates and becomes a water in soluble salt entrapped within the polymer matrix of the lens. Finally, a sodium bicarbonate solution also of substantially 5% concentration is applied to neutralize the sulfuric acid previously applied during the oxidation phase or process. Following the addition of the sodium bicarbonate solution, the lens may be removed from the fixture, cleaned with a suitable cleaner and subjected to a heat disinfection cycle prior to dispensing to the patient.
As mentioned previously, such a process has heretofore required relatively complex and expensive equipment, as well as extensive handling of the contact lenses and/or fixtures by skilled, trained personnel, during the tinting process. Hence, such tinting has heretofore been carried out primarily by contact lens manufacturers having the proper equipment and trained personnel to complete the tinting process. Accordingly, patients wishing tinted contact lenses must initially be fitted for lenses by a qualified eye care specialist, and thereafter lenses of the desired color must be ordered from the lens manufacturer.
Hence, the patient must wait for some period of time to receive the desired tinted lenses. However, many eye care specialists may desire to dispense tinted lenses directly to the patient, thus more quickly achieving the desired vision correction and desired cosmetic improvement during but a single office visit. However, heretofore such immediate dispensing of tinted lenses has not been possible.